Heide also started having episodes of breathlessness. Finally, a pulmonologist diagnosed her with asthma and prescribed a course of prednisone, a steroid. Two days later, she was feeling—and breathing—much better.

We tend to think of asthma as something that’s diagnosed in childhood, but it’s not uncommon for women especially to develop the condition as an adult. However, adults often don’t realize it — they write off a persistent cough or other symptoms like wheezing or shortness of breath, saying it’s just allergies or the lingering effects of a recent cold.

In fact, allergies are often the culprit. The Asthma and Allergy Foundation of America estimates that allergies trigger at least 30 percent of adult asthma cases. Sustained exposure to certain substances in the workplace or your environment can also contribute.

How can you tell the difference between a cold or allergies and asthma? Watch for symptoms like Heide’s cough that hang on for a long time, or more frequent-than-usual bouts of bronchitis in the winter.

“At some point, it crosses a threshold where it might be worth some investigating,” says Dr. David Beuther, a pulmonologist with National Jewish Health in Denver.

Your doctor may recommend a lung function test, which uses a device called a spirometer to measure how much air you can exhale, and how fast. That will help pinpoint the best course of treatment based on the severity of your case.

And take heart—you don’t have to give up exercising. (Heide remains an avid tennis player.) Dr. Andy Nish, a spokesman for the American Academy of Allergy Asthma and Immunology, usually recommends that all newly diagnosed patients use a bronchodilator before exercising.

“If they have been exercising with no symptoms at all, or, over time, note that they do fine without using their bronchodilator pre-exercise, then they may not need to,” he says.

There’s no foolproof way to avoid developing adult-onset asthma, but there are a few steps you can take to reduce your chances:

· Just say no to cigarettes. “The No. 1 (trigger) would certainly be smoking,” says Beuther, who also recommends avoiding situations that expose you to secondhand smoke.

· Get a flu shot. Viral infections often trigger asthma, but there’s unfortunately not a lot you can do about them. But a flu vaccination will ward off at least one cough-and-wheeze-inducing virus per season.

· Reduce your exposure to allergens. Nish suggests putting dust-mite covers on your pillows and mattress if you’re allergic to dust mites, or keeping furry pets out of your bedroom if you have a pet allergy.